Problem: Kevin is 32 years older than Daniel. Four years ago, Kevin was 5 times as old as Daniel. How old is Daniel now?
Explanation: We can use the given information to write down two equations that describe the ages of Kevin and Daniel. Let Kevin's current age be $k$ and Daniel's current age be $d$ The information in the first sentence can be expressed in the following equation: $k = d + 32$ Four years ago, Kevin was $k - 4$ years old, and Daniel was $d - 4$ years old. The information in the second sentence can be expressed in the following equation: $k - 4 = 5(d - 4)$ Now we have two independent equations, and we can solve for our two unknowns. Because we are looking for $d$ , it might be easiest to use our first equation for $k$ and substitute it into our second equation. Our first equation is: $k = d + 32$ . Substituting this into our second equation, we get the equation: $(d + 32)$ $-$ $4 = 5(d - 4)$ which combines the information about $d$ from both of our original equations. Simplifying both sides of this equation, we get: $d + 28 = 5 d - 20$ Solving for $d$ , we get: $4 d = 48$ $d = 12$.